1. Field of the Invention
The present invention relates to a valve for switching oil passages, and more particularly to an oil filter used in the valve for preventing foreign particles contained in oil from entering into the switching valve.
2. Description of Related Art
An example of this type of valve is disclosed in JP-A-2000-346006. Oil having a predetermined oil pressure is supplied to an actuator, such as a variable-valve-timing mechanism for an internal combustion engine, through an oil passage switching valve. The oil is supplied to either a chamber for advancing the valve timing or a chamber for retarding the valve timing by switching the oil passages. The valve is composed of a valve portion and a driving portion for electromagnetically driving a valve body contained in the valve portion. In this type of valve, it is necessary to prevent foreign particles contained in the oil from entering into an inside space of the valve. For this purpose, in the conventional valve system, an oil filter is disposed in an oil passage connecting the valve and the engine.
In the conventional valve system, it is difficult to prevent foreign particles generated in the oil passage between the oil filter and the valve from entering into the valve chamber. Accordingly, it is preferable to dispose the oil filter at a position closest possible to the valve. However, the position of the oil filter is not freely chosen due to restriction from a piping layout.